This invention relates generally to expansion-type bolts, and more particularly, to a sleeve anchor of the type having a bolt and an expansion sleeve longitudinally shiftable upon tightening of the bolt to wedge the sleeve anchor within a hole or recess in rock, concrete, solid concrete block, hollow concrete block, grout-filled hollow concrete block, mortar joints, brick, masonry or other like material.
A sleeve anchor is a species of anchor bolts, wherein a metal sleeve extending along a bolt is caused to shift upon tightening of the bolt for tightly expanding within a hole bored into concrete, concrete blocks, masonry and various materials of this character. The anchor is thus used for securement of extrinsic structures, such as building materials, shelving, structural members and so forth. Such devices are customarily employed in many fields, including construction as well as for the fastening of machinery and equipment to masonry or rock structures.
As conventionally configured, the bolt includes a wedge-defining portion which causes outward expansion of the sleeve upon tightening of the bolt. An example is disclosed in Lerich U.S. Pat. No. 3,750,526. Also representative of the prior art are Lerich U.S. Pat. No. 3,750,519 and Oettl U.S. Pat. No. 4,334,813.
The key element in a sleeve anchor is the expansion sleeve which compresses the concrete, or other hard material as the bolt or so called stud is partially withdrawn from the hole upon tightening of a nut, inasmuch as the expansion sleeve configuration is determinative of the performance character of the anchor in the areas of setting of the anchor within the hold, tensile performance (i.e., the anchoring capability or ultimate tensile strength when secured), and ultimate failure mode.
Heretofore, conventional sleeve anchors have exhibited difficulties in enabling the sleeve anchor to be installed and to be "set" in the hole. Conventionally, the sleeve provides a springy slip fit in a typical hole and such does not provide enough friction to prevent the sleeve from rotating within the hole upon tightening, as well as sometimes permitting the anchor to slide out of the hole. Further, in hollow concrete block installations, where little of the exposed surface material of the sleeve will bear against the internal surfaces of the hole, slippage is frequently encountered, resulting in substantial installation difficulties. Matters are rendered more difficult by the need to provide for both resistance to rotation as well as withdrawal for the anchor when originally inserted into the hold, prior to tightening.
A further requirement and desirability for structural anchors is the ability to pre-load; that is, to positively clamp a fixture to the substrate or base material in which the hole is provided. Without pre-loading with development of clamping force for so affixing the fixture to the substrate, any tensile load upon the structure will result in immediate fixture looseness and/or strain. When pre-loading is to be provided, the tensile force developed or exerted by the structure upon the anchor, as tightened, must exceed the pre-load in order for looseness and/or strain to occur. The ability to pre-load beyond the normal working load of a sleeve anchor ensures that it will provide proper structural performance. In other words, there should not result any looseness or strain at normal working loads.
Accordingly, among the several objects of the present invention may be noted the provision of an improved sleeve anchor; the provision of such an anchor which, when inserted in a hole in concrete, masonry or other building materials, will set reliably therein to prevent rotation or withdrawal until tightening of the anchor; the provision of such an anchor which provides pre-loading upon tightening to positively clamp a fixture to the substrate or base material, namely the concretee, masonry, or other building material receiving the anchor, and providing pre-loading beyond the normal working load of the sleeve anchor so that tensile forces must exceed the pre-load capability for looseness and/or strain to occur; the provision of such a sleeve anchor which provides pre-loading such as heretofore normally associated only with stud anchors; the provision of such a sleeve anchor having far greater pre-loading than heretofore possible; the provision of such a sleeve anchor which has a higher ultimate tensile strength than other sleeve anchors, and particularly through use of an expansion sleeve that develops the full strength of the substrate material, such as concrete, masonry and so forth, and the provision of such a sleeve anchor having a sleeve uniquely configured for development of maximum compressive forces for confirmation with the circumference of the stud thereof for reliable and secure maintenance within the substrate hole upon tightening; and the provision of such a sleeve anchor which is not prone to catastrophic anchor failure, reliably providing ultimate tensile value even under strain.
Briefly, a sleeve anchor in accordance with the invention for use in a pre-drilled hole in concrete, masonry and the like, comprises a bolt including a threaded outer end for receiving an internally threaded pressure member, such as a tightening nut, and an inner end defining a shank extending from the outer end and terminating in a head of greater diameter than the shank. The head has a tapered wedge-forming shoulder adjacent to the shank, the head constituting the leading edge of the anchor for being inserted in the hole with the threaded outer end extending from the hold for receiving the tightening nut for tightening by its rotation. A sleeve is disposed concentrically on the bolt. The sleeve is formed to include a collar positioned concentrically around the bolt and extending along a portion of its threaded portion at the upper end thereof. The collar is disposed for receiving longitudinal pressure toward the inner end of the bolt generated by tightening of the tightening screw. The collar includes an inner portion of petalform configuration comprising three petals extending along the shank and closely-spaced side-by-side but separate relationship to surround the shank. The petals are joined at proximal ends to the collar by respective pillars, each of narrow arcuate extent, to provide windows between the pillars. Such windows are of arcuate extent greater than each pillar. Distal end of the petals contact the end of the shoulder such that upon tightening of the pressure tightening screw, the petals are caused to ride up the shoulder for radially outward expansion of the sleeve within the hole. The distal ends of the petal each form in section a central arc and straight portions extending from opposite ends of the arc thereby to provide for each petal a vee-shaped lobal prominence of approximately 90.degree. included angle, whereby the distal ends of the petals together form in section an enhanced hexagon of trilobular configuration. Each petal forms at its proximal end a single ear disposed along the leading side edge thereof, the ear being constituted by an outwardly extending corner portion of the respective petal. The ears provide gripping anti-rotational engagement of interior surfaces of the hole upon insertion of the anchor into the hole to prevent rotation of the sleeve therein upon rotation of the tightening screw. The sleeve is formed of resilient ultimately deformable metal to permit flexing of the ears and the distal ends of the petals to permit torsional distortion of the pillars upon continued tightening of the tightening screw caused by pressure between the opposite ends of the sleeve. Such causes pre-loading of the anchor within the hole.
Other features will be in part apparent and in part pointed out hereinbelow.